CActor: Make Render() a non-const function

A few implementations of Render() contain const-casts nested within its
their call hierarchy to get around the fact that this function is marked
const. We can just make the member function non-const to allow removal
of these casts in follow up changes.

Runtime/MP1/World/CPuddleSpore.cpp

@@ -134,7 +134,7 @@ void CPuddleSpore::Think(float dt, CStateManager& mgr) {
   CPatterned::Think(dt, mgr);
 }
 
-void CPuddleSpore::Render(const CStateManager& mgr) const {
+void CPuddleSpore::Render(CStateManager& mgr) {
   CPatterned::Render(mgr);
   if (x56c_ > 0.01f) {
     for (const auto& elemGen : x5dc_elemGens)